Crown-Abutment Interfaces in Implant-Supported Restorations - A Review

Abstract The crown-abutment interface is a critical determinant of the long-term success of implant-supported restorations, influencing mechanical stability, resistance to bacterial infiltration, and overall biological compatibility. This review examines the evolution of interface designs, from early external hex systems - prone to mechanical complications such as screw loosening-to advanced internal connection systems, including conical and Morse taper designs, which offer improved structural integrity and reduced micro-movement. Beyond traditional cement-retained and screw-retained methods—each with distinct advantages and limitations—emerging alternatives such as hybrid abutments, conometric retention systems, and shape-memory alloy solutions are gaining attention. Hybrid abutments, combining a titanium base with a ceramic suprastructure, provide an optimal balance of strength and aesthetics. Meanwhile, conometric and shape-memory retention systems introduce innovative approaches that eliminate the need for conventional screws or cement, potentially reducing complications associated with microleakage and excess cement. Although long-term clinical studies demonstrate high survival rates across different interface designs, variations in complication rates underscore the need for ongoing research and refinement. The selection of a crown-abutment interface should be guided by a comprehensive evaluation of mechanical, biological, and esthetic considerations to optimize long-term restoration performance and patient outcomes.